This invention relates to an austenite alloy tube having an excellent high temperature vapor oxidation resistant property and contemplates improvement of high temperature steam oxidation resistant property of an austenite alloy tube including an austenite stainless steel tube utilized in a boiler or the like and subjected to high temperature steam thereby decreasing the amount of scale formed by high temperature steam.
As is well recognized in the art an austenite stainless tube utilized in a boiler forms a large quantity of scale on the inner surface of the tube owing to the oxidation action of steam at a temperature of 500.degree. C. to 700.degree. C., usually 550.degree. C. to 650.degree. C. The scale thus formed peels off due to the difference in the thermal expansion coefficients of the tube and the scale at the time of starting and stopping the boiler thus causing trouble during the boiler operation. Heretofore, various proposals have been made to prevent formation of oxide scale caused by high temperature steam. Among these proposals are included a method of plating chromium on the inner surface of the tube, use of an alloy containing a large quantity of chromium (for example, 25% chromium--20% nickel steel) or fine grain steel and a method of subjecting the tube inner surface to shot working. Among these only the fine grain steel and shot working have been practically used.
However, even when fine grain steel (for example SUS347 steel) is used it is not always effective and its type is limited. Alloys subjected to shot working greatly decreases its advantageous effect when subjected to high temperature hysteresis. Although various methods of decreasing the disadvantage have been investigated, crystal size and degree of working are limited.